Bumpers are used on motor vehicles to absorb low level impact forces and to limit the amount of damage sustained to the vehicle body during high level impacts. In an attempt to achieve this objective, many of the known bumper systems have necessarily resulted in arrangements involving an undesirably large size or space requirement, and in addition have resulted in undesired structural complexity and cost. In addition, it is believed that most such bumper systems have failed to provide for maximum energy absorption resulting from an impact, particularly in relationship to the overall size, weight, cost and protectability of the known bumper systems.
Conventional design practice is to provide a bumper system having a single armature (i.e., a simple beam) which, when impacted, absorbs energy by permitting buckling (i.e., plastic deformation) at locations concentrated at the vehicle centerline of the beam and at the locations where the beam mounts to the vehicle. This arrangement of the simple beam, however, provides an inefficient energy absorbing capability, and hence the bumper system is conventionally provided with separate energy absorbers such as struts, springs or foam members which cooperate with the beam. This conventional design is thus complex and requires significant space to package it on a vehicle, and generally results in an inefficient use of material and often results in a system having significant weight.
The present invention relates to an improved bumper system for a vehicle which attempts to improve on conventional prior art constructions by providing a multiple-beam bumper system which, in conjunction with the connections to the vehicle, define multiple fulcrum points so that the bumper system is effectively defined by multiple beams which permit more effective absorption of energy, as caused by an impact against the bumper, due to relative movements of the beams and the permissible plastic energy-absorbing deformations which occur within the bumper system.
The bumper system of the present invention, as aforesaid, in addition to permitting more effective dissipation of energy within the bumper system prior to the ending of an external impact event, is also believed to represent a bumper system solution which can be more readily and less expensively manufactured and can be incorporated into a smaller package depth by permitting more energy to be dissipated per unit distance of impact intrusion.
In the improved vehicle bumper system of this invention, the system is defined principally by outboard (i.e. front) and inboard (i.e. rear) elongate beams which project transversely across the vehicle. The ends of the front and rear beams are joined by connecting points which function as energy-absorbing fulcrums or hinges, with the remainder of the front and rear beams initially being free of direct structural connection. The front beam is preferably of an outwardly curved configuration so that the center portions of the front and rear beams define a horizontal space or gap therebetween. The rear beam defines the structural connection to the vehicle, and in particular the rear beam at two points disposed on opposite sides of the vehicle longitudinal centerline, and spaced transversely inwardly from the end connections, is joined to mounting elements or rails on the vehicle by connections which define inboard fulcrum or hinge points. The front and rear beams are each preferably formed as elongate monolithic structures, such as of high strength steel, and have configurations which enable them to nest one within the other in the longitudinal direction of the vehicle. For example, one of the beams is preferably of a C-shaped cross section, and the other beam is of a compatible C-shaped or hollow rectangular configuration to enable the two beams to at least partially nest. The two beams, in the nondeformed condition, have the end parts thereof nested together to define the outboard connections thereat. An external impact against the front beam can effect rearward deflection thereof and transmission of energy along the front beam to the outboard connections, which in turn effect energy absorption at the end beam portions of the rear beam which project between the inboard and outboard connections. This also causes the center portion of the rear beam to deflect forwardly toward the front beam to effect additional energy absorption, with the front and rear beams being moved toward one another for more effective nesting engagement so that the two beams ultimately act as one so as to permit additional absorption of the impact energy. Additional connecting blocks can be provided for cooperation between the front and rear beams if desired.
In the improved bumper system of the present invention, as aforesaid, the front and rear beams and their connections to one another at the outboard ends, and the connection of solely the rear beam to the vehicle at the inboard connection points, effectively define a kinematic structure having four connection points which function similar to fulcrums in that they permit energy-absorbing relative motion between the front and rear beams, and between the rear beam and the vehicle frame, with the energy absorption being in various stages as the impact event progresses. Further, the four connection points effectively cause the front and rear beams to define a four-beam system, with the rear beam having three beam portions due to the pairs of inboard and outboard connection points. This in addition enables the center beam portion of the rear beam to undergo outward bowing or deflection (i.e. away from the vehicle) toward the front beam during an impact event so as to improve the energy-absorbing capabilities while at the same time minimizing or delaying the impact of the bumper against the remainder of the vehicle.
Other objects and purposes of the improved bumper system according to the present invention will be apparent to persons familiar with systems of this general type upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following descriptions for convenience in reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The word “front” will refer to a direction which faces away from the vehicle end, namely upwardly in FIG. 2, and the word “rear” will refer to the opposite direction. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the bumper system and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.